1. Field of the Invention
The present invention relates to a motor control apparatus, and more particularly, to a motor control apparatus in which a power supply to drive other components is employed in braking a motor without an additional power supply.
2. Description of the Related Art
A three-phase motor has three windings and is driven by three-phase power. To control the three-phase motor, a motor control apparatus, as shown in FIG. 1, comprises a controller power supply 160 to supply power to an inverter controller 122 and a braking controller 124, an inverter 110 to supply the three-phase power to a motor 100, an inverter controller 122 to control the inverter 110 to generate the three-phase power, a braking circuit part 130 to brake the three-phase motor 100, and a braking controller 124 to output a braking signal to brake the three-phase motor 100 to the braking circuit part 130.
The inverter 110 converts DC (direct current) power into three-phase AC (alternating current) power and supplies the three-phase AC power to the three-phase motor 100, wherein the DC power is supplied through a rectifying part (not shown) and a capacitor (not shown) which rectify and smooth commercial AC power of an AC power supply (not shown). Here, the inverter 110 comprises a plurality of transistors 120 and a plurality of diodes 140.
The inverter controller 122 operates at a voltage of 5V and selectively turns on/off the transistors 120 of the inverter 110, thereby controlling the inverter 110 to convert the DC power into the three-phase AC power.
The braking circuit part 130 includes a relay part 132 closing and opening so as to control a supply of braking power from a braking power supply 170 to the three-phase motor 100, and a braking condenser 134 to store the braking power supplied from the braking power supply 170. Further, the braking power supplied from the braking power supply 170 via the braking condenser 134 generally has a voltage of 24V. The relay part 132 is closed/opened by a relay driving circuit 132a according to control by the braking controller 124.
Further, the braking circuit part 130 comprises a braking diode 136 to prevent a voltage spike generated a moment when the relay part 132 is opened from being supplied to the braking power supply 170, and a freewheeling diode 137 to bypass a current remaining in the three-phase motor 100 when the three-phase motor 100 is disconnected from the braking circuit part 130 by, for example, a disconnection of a connector 138.
However, in the conventional motor control apparatus, the power supplied to the inverter controller 122 and the braking controller 124 is different from that supplied to the braking circuit part 130 in a voltage thereof, so that the braking power supply 170 is further provided to generate the braking power to brake the three-phase motor 100. Therefore, a production cost and a size of a product are increased for the conventional motor control apparatus.